Colors are excellent! Nicely done. Whatever you're using for lighting and post processing is working, don't change it!
Looks like your shutter speed is a little too slow to counter the flow going on in your tank. Either turn up ISO (if you camera can hang with it) or turn off your powerheads to compensate. It's worth noting that on all lenses (esp cheaper lenses), working at either extreme for aperture will absolutely drastically affect sharpness of your image. If that's something you're after, you may want to consider experimenting with different focal lengths and distances from your subject to get the whole thing in focus vs. taking aperture to extremes.
Also, if you shoot at odd angles against the glass (i.e., camera lens is pointed at 45 deg angle from the glass), your focal plane will be skewed or altered and you will find odd distortion and focus issues in your images. It's best to try to shoot straight-on to avoid these issues (of course sometimes that can't be helped).
Great shots